The present invention relates to an organic electronic device including a charge-injection-type luminescence device having an organic active layer and a drive circuit therefor formed integrally on a common substrate, and also a nonlinear device having an organic layer therefor.
As a charge injection-type luminescence device, a light-emitting diode (LED) using an inorganic single crystal of CaAs, GaP, GaN, etc., has been widely used, but research work on organic luminescence materials has also been made for a long time. For example, Pope, et al., reported an electric field luminescence phenomenon by using an anthracene single crystal in 1963 (J. Chem. Phys. 38 (1963) 2042). Further, Helfrich and Schneider succeeded in observation of relatively strong EL (electroluminescence) by using a solution electrode system in 1965 (Phys. Rev. Lett. 14 (1965) 229).
Thereafter, various studies for providing organic luminescence materials have been made as reported in, e.g., U.S. Pat. Nos. 3,172,762; 3,173,050; 3,710,167; J. Chem. Phys. 44 (1966) 2902: J. Chem. Phys. 50 (1969) 14364; J. Chem. Phys. 58 (1973) 1542 and Chem. Phys. Lett. 36 (1975) 345, but devices of commercial level have not been provided because of problems, such as weak luminescence intensity and necessity of high voltages for luminescence.
In recent years, however, Tang, et al., have developed an organic EL device comprising very thin vacuum deposition layers (a charge-transporting layer and a luminescence layer) and have realized a high luminance at low drive voltages (Appl. Phys. Lett. 51 (1987) 913 or U.S. Pat. No. 4,356,429). This lamination type of organic luminescence devices have been actively studied since then, and the possibility of various applications thereof, including a flat panel display, is becoming practical recently.
FIG. 9 shows a representative laminate structure of such an organic EL device, including a substrate 500; a transparent electrode 501 comprising indium/tin oxide (ITO) and functioning as an anode of an organic EL device as a luminescence device; a hole-transporting layer 502 comprising an organic hole-transporting material, such as an aromatic diamine as represented by formula (1) below; an electron-transporting layer 503 comprising an electron-transporting material, such as tris(8-quinolynol)-aluminum complex (or tris(8-quinolynalato)aluminum complex) generally identified as Alq3, is represented by formula (2) below; and a cathode 504 comprising a material having a low work function, such as Al or Mg:Ag alloy. 
When a voltage is applied between the anode 501 and the cathode of the organic EL device, holes injected from the anode 401 into the hole-transporting layer 502 and electrons injected from the cathode 504 into the electron-transporting layer 503 (optionally via an optional electron-injection layer) are recombined to cause luminescence.
When such an organic EL device is applied to a flat panel display, it is necessary to arrange a plurality of pixels each comprising such an organic EL device and control the luminescence at the respective pixels independently. For this purpose, it is the simplest way to form a simple matrix structure by forming a plurality of parallel anode stripes on a substrate, forming thereon organic layers including a hole-transporting layer and an electron-transporting layer, and forming thereon a plurality of parallel cathode stripes intersecting with the anode stripes at right angles so as to form a pixel at each intersection of the anodes and the cathodes. For driving the simple matrix device, the mutually parallel cathodes are sequentially connected one at a time to a negative power supply with the other cathodes open, and in synchronism therewith, the anodes are selectively connected to a positive power supply or made open. As a result, only when a certain cathode is connected to the negative power supply, the respective pixels on the cathode are selectively turned on or off depending on whether or not the associated anodes are connected to the positive power supply.
This drive system is simple but is accompanied with a difficulty that the pixel lighting duty is lowered if the number of cathode lines are increased, since in the system only one among the plurality of cathode lines is connected to the negative power supply at a certain instant, and only the pixels on the line are selectively turned on or off depending on whether or not the associated anodes are connected to the positive power supply and the other pixels are extinguished regardless of whether the associated anodes are connected or not. As a result, even if a high luminance is attained at the instant of turn-on, an effective luminance as an average over a certain period is lowered if the number of cathode lines are increased corresponding to an increased number of pixels.
For obviating the above problem, an organic EL device equipped with a transistor at each pixel has been proposed. FIG. 10 is an equivalent circuit diagram of one pixel of such an organic EL device.
Referring to FIG. 10, a pixel unit includes a first thin film transistor (address transistor) 601, a storage capacitor 602, a second thin film transistor (drive transistor) 603, an organic EL device 604 functioning as an organic EL element 604 as a luminescence element, an electrode Pd connected to a source electrode of the address transistor, an electrode Pc connected to a second side of the storage capacitor 602 and a gate electrode of the drive transistor 603, an electrode Ps connected to a gate electrode of the address transistor 601, an electrode Pv connected to a first side of the storage capacitor 602 and a source electrode of the drive transistor 603, and an electrode Pled connected to a cathode of the organic EL element 604.
Ps is supplied with a selection signal, Pd is supplied with a data, and at Pc is developed a potential depending on the data signal by the charging and discharging of the storage capacitor 602. Pv and Pled are placed at fixed potentials.
The circuit operates as follows.
When a selection signal supplied to Ps is placed in a selection state (xe2x80x9chighxe2x80x9d), the potential at Ps is raised. As a result, the source-drain channel of the address transistor 61 is made conductive so that a current corresponding to a data signal supplied to Pd is flowed to the storage capacitor 602, whereby a potential difference between the source electrode and the gate electrode of the drive transistor 603, i.e., a potential difference between Pv and Pc, becomes a value corresponding to the data signal supplied to Pd. Accordingly, a current corresponding to the data signal flows through the drive transistor 603 so that the organic EL element 604 causes luminescence at a luminance corresponding to the data signal. When the selection signal supplied to Ps is placed in a non-selection state (xe2x80x9clowxe2x80x9d), the source-drain channel of the address transistor is made non-conductive, no current flows to the storage capacitor 602 even when the data signal supplied to Pd is changed, so that the potential difference between Pc and Pv is not substantially changed and the luminescence at the organic EL element is not substantially affected thereby.
In such an organic EL device, as described above, each pixel is equipped with an address transistor, a drive transistor and a storage capacitor, and a charge corresponding to a data signal in a selection period is stored at the storage capacitor, whereby the organic EL element at the pixel continually causes luminescence corresponding to the stored charge even in the non-selection period. Accordingly, there is attained an advantage that the luminescence duty at each pixel is kept high without causing a lowering in effective luminance even if the entire device includes a large number of pixels.
The transistors disposed at each pixel are ordinarily thin film electric field-type transistors made of polysilicon or amorphous silicon.
However, in order to form such an organic EL device, after a whole process of forming a thin-film transistor made of polycrystalline silicon or amorphous silicon on a substrate, it is necessary to further apply a process of forming organic EL elements. The thin-film transistor forming process includes a time-consuming step of depositing an amorphous silicon film by a plasma CVD apparatus and a troublesome and time-consuming step for converting the deposited amorphous silicon film into a polysilicon film by laser light scanning for annealing of the amorphous silicon film and this is a substantial cost-increasing factor.
In view of the above, a method of forming a pixel transistor with organic layers has been proposed so as to simplify the process compared with the conventional method of forming transistors with amorphous or polycrystalline silicon.
In order to produce also a transistor with organic layers, an organization as described below may be conceived of.
FIG. 11 is a schematic partial plan view showing on pixel region of such an organic EL device, including a first transistor (address transistor) 701 constituting the pixel, a storage capacitor 702, a second transistor (drive transistor) 703 and an organic EL element 704 as a luminescence element.
FIG. 12 is a partial sectional view of an Axe2x80x94Axe2x80x2 section in FIG. 11 of the organic EL device, including the first transistor 701, (the storage capacitor 702), the second transistor 703 and the organic EL element 704.
The first transistor 701 functioning as an address transistor includes a gate electrode 801 comprising Cr, a gate insulating layer 802 comprising SiO2, an active layer 803 comprising oligo-thiophene represented by e.g., a structural formula (3) shown below, and a source electrode 805 and a drain electrode 806 respectively comprising Au. The second transistor 703 functioning as a drive transistor includes a gate electrode 801 comprising Cr, a gate insulating layer 902 comprising SiO2, an active layer 903 comprising oligo-thiophene, and a source electrode 905 and a drain electrode 906 comprising Au. The organic EL element 704 functioning as a luminescence element includes a transparent electrode 1001 functioning as an anode comprising indium/tin oxide (ITO), a hole-injection layer 1002 comprising copper-phthalocyanine represented by formula (4) shown below, a hole-transporting layer 1003 comprising an aromatic diamine as mentioned above, an electron-transporting and luminescence layer 1004 comprising tris(8-quinolynol)aluminum complex as mentioned above, an electron-injection layer 1005 comprising LiF and a cathode 1006 comprising Al. 
By adopting a structure as illustrated in FIGS. 10 and 11, drive transistors can be formed of without using inorganic semiconductors, such as amorphous or polycrystalline silicon, to obviate a time-consuming and expensive process attributable to the device-forming process using such amorphous or polycrystalline silicon.
However, according to the device structure including an organic transistor as illustrated in FIGS. 10 and 11, charges have to be transferred over a long distance through an active organic layer in a planar direction. As organic materials generally show a low carrier mobility, the requirement for a higher mobility organic material narrows the latitude of material selection and has provided an obstacle for commercialization.
In view of the above-mentioned problems, a principal object of the present invention is to provide an organic electronic device including an organic luminescence device and a drive means therefor, which is easy to produce, highly reliable and inexpensive.
Another object of the present invention is to provide a nonlinear device which has a function corresponding to an organic transistor as mentioned above, can be formed by using not a special organic material exhibiting a remarkably high mobility but an organic material selected from a broader class, and is therefore suitable as a drive means for the above-mentioned organic electronic device.
According to the present invention, there is provided an organic electronic device, comprising a common substrate; an organic luminescence device formed on the common substrate and comprising an anode, a cathode and an organic luminescence layer disposed between the anode and cathode; and a nonlinear device formed on the common substrate for controlling a current flowing to the organic luminescence device;
wherein the nonlinear device has a structure including a first organic layer and a second organic layer each comprising an organic material, and at least one metal layer principally comprising a metal element and sandwiched between the first and second organic layers so as to flow at least a part of current flowing through the metal layer between the first and second organic layers sandwiching the metal layer.
The present invention further provides a nonlinear device, having a laminate structure including a first electrode, a first organic layer, a metal layer, a second organic layer and a second-electrode successively disposed on a substrate.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.